I think this threat should be split up but…
I don't own much games on this platform but I recall few sample scenarios I had problems with:
1. For a long while there was no support for Poland and I was using UK account I had created when I was staying in London. When it was announced that Poland is finally OK I created Polish account for myself. There was no account transfer procedure these days so I had two of them. Sadly, it quickly appeared that many games I have (bought in Poland) were not handled by Polish account. They were "not supported in my region". BS I say: it was "normal" to go to shop in Poland, buy game and see it is not handled at all on Polish account. When transfer option arrived I moved my UK account - it had more games. Since joining two profiles is not possible I had to abandon poor one. I could have it but fun thing is: they both were created for the same email address and MS support was not able to even help me to log in into "first PL" one….
2. Many times in the past I had issues with WL client updates. Everything was working fine, an update and crashes after that. Each time I had to re-install their client application. After that: all my saves are flying away. Last time it happened: I almost finished Batman. Oh! And stupid crap is: if you play off-line, your savegames will be deleted first time you go live.
3. DLCs are joke. For many games GFWL shows I have them downloaded and installed but they cannot be reached from within games (i.e. Dead Rising 2). Or in-game manager says nothing is available but everything is working fine during gameplay (i.e. Fable 3). I know it may be issue with specific games but sometimes client says nothing exists but game sees it.
4. Although Lost Planet 2 works darn good on co-op, Gears (with UK friend) - too, some titles (Fable 3, Dead Rising 2) are laugh in face with serious connectivity issues or non-achievable achievements (Fable 3).
5. Voice support is bad, so bad that I always have to use Skype for it. GFWL client's voice quality feels like listening to vinyl music next to jackhammer in traffic jam.
6. I am still using WinXP and I wonder how long it is until an update for "Vista up only" comes.
This rant is PC-only. Only Xbox experience I have is split-screen co-op in Gears of War 2 - seemed OK for friend.
I am not sure about "premium only online play" rumours though.
I have about hundred games on Steam and few of them are troublesome for me (i.e. neither Portal 2 nor Saints Row 3 work on my home PC) but it is GFWL for which I felt more furious.
Stats: for ~100 games on Steam I have problems with about 10. For almost 10 GFWL titles - 5 problematic. Ratio is not helpful.